1. Field of the Invention
The present invention relates to monolithic capacitors. In particular, the present invention relates to a monolithic capacitor that includes a laminated body including a plurality of dielectric layers stacked on each other; a plurality of capacitor electrodes disposed in the laminated body to face each other, with each of the dielectric layers interposed between adjacent ones of the capacitor electrodes; and a plurality of outer electrodes disposed on the surface of the laminated body and connected to the capacitor electrodes.
2. Description of the Related Art
In a monolithic capacitor formed by alternately stacking dielectric layers and capacitor electrodes, the application of a voltage thereto causes electrostriction in capacitive portions and expansion and contraction of a laminated body. In recent years, as monolithic capacitors have become smaller and their layers have become thinner, the intensity of an electric field applied to the dielectric body has increased and the resulting electrostriction has become difficult to ignore. When a voltage including ripples, i.e., an alternating (AC) voltage, or a direct (DC) voltage having an alternating-current component superimposed thereon is applied to a monolithic capacitor mounted (or soldered) on a substrate, the expansion and contraction of a laminated body propagates to the substrate and causes the substrate to vibrate. The resulting noise is perceived by the human ear when the frequency is in the audible range of about 20 Hz to about 20 kHz. This noise, which may be referred to as “acoustic noise”, causes problems in television sets, notebook computers, and cellular phones.
Various techniques have been proposed to prevent or reduce such “acoustic noise”. For example, Japanese Unexamined Patent Application Publication No. 2000-232030 proposes a technique in which ceramic capacitors having the same specifications are disposed on the respective front and back surfaces of a circuit board such that they are plane-symmetric with respect to the circuit board. In this technique, a vibration transmitted from one capacitor to the circuit board and a vibration transmitted from the other capacitor to the circuit board cancel out each other to reduce audible sound.
However, the technique described in Japanese Unexamined Patent Application Publication No. 2000-232030 requires two capacitors of the same specifications to be mounted on the front and back surfaces of the circuit board. This restricts the degree of freedom in circuit design.